Apparatus to control the feeding amount in bandsawing machines

ABSTRACT

Apparatus to control the feeding amount in hydraulically controlled band sawing machines having a pivotable frame which supports the bandsaw, and a hydraulic cylinder for lifting and lowering the frame with respect to the material to be cut, comprising a hydraulic pressure control means for the cylinder, valve means (preferably with a knife-edge shaped outlet) for controlling the quantity of hydraulic fluid reaching the cylinder, and at least one hydraulic connection, namely between the outlet of the control means and the inlet of the valve means.

United States Patent Tsuneo Aizawa Isehara-Cho, Japan Appl. No. 710,839

Filed Mar. 6, 1968 Inventor Patented Apr. 13, 1971 Assignee Amada Co., Ltd.

Tokyo, Japan Priority June 12, 1967 Japan 42/37241 APPARATUS TO CONTROL THE FEEDING AMOUNT IN BAND SAWING MACHINES 6 Claims, 6 Drawing Figs.

US. Cl 83/201116, 8 3/5 64 Int. Cl 826d 1/46 Field of Search 83/201 .06,

[5 6] References Cited UNITED STATES PATENTS 1,390,469 9/1931 Stowell 83/20 1.06 2,601,576 6/l952 Wells et al. 83/20L06 Primary Examiner-James M. Meister Attorney-Cecily L. Frey ABSTRACT: Apparatus to control the feeding amount in hydraulically controlled band sawing machines having a pivotable frame which supports the bandsaw, and a hydraulic cylinder for lifting and lowering the frame with respect to the material to be cut, comprising a hydraulic pressure control means for the cylinder, valve means (preferably with a knifeedge shaped outlet) for controlling the quantity of hydraulic fluid reaching the cylinder, and at least one hydraulic connection, namely between the outlet of the control means and the inlet of the valve means.

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APPARATUS TO CONTROL THE FEEDING AMOUNT IN BAND SAWING MACHINES This invention is concerned with an apparatus and a method to control the feeding amount, i.e., the cutting-in speed of band sawing machines.

In a conventional band sawing machine, well-known needle valves have been used so far as quantity control valves for the oil flow out of the hydraulic cylinder which controls the lowering of the frame for the bandsaw. Generally, however, the oil pipe of the needle valve is so narrow that viscosity changes greatly influence the oil flow due to friction with the pipe wall. For instance, oil flow is relatively small when oil temperature is low at the starting of the cutting operation, while on the contrary oil flow becomes more intensive when oil temperature is high. Thus there has been the problem that the cutting-in speed increases gradually in spite of the constant throttling effect of the quantity control valve.

As a second problem, conventional band sawing machines have been constructed basically under the technical concept that the total cutting load of the saw blade should always be kept constant; consequently, for instance, there has been the disadvantage that, in case when the cutting length becomes gradually shorter, the load per unit length increases and the cutting-in speed increases. Thus in case of thin materials the cutting-in speed increases too rapidly, causing damage to the saw blade, and in case when the cutting length becomes too long or a hard material is to be cut, the cutting-in speed decreases, causing the saw blade to wear at its edge, and making its life shorter. Furthermore, this influences negatively the efficiency of operation.

This invention is aimed at solving the above-mentioned problems. Firstly the outlet side of the control valve is formed into a knife-edge shape so as to lessen the influence of viscosity variation. Thus, the oil volume passing through the quantity control valve is always kept at a level to correspond to the opening of said valve irrespective of the variation of oil temperature, whereby the variation of the cutting-in speed is controlled.

Secondly a mechanism for controlling and reducing oil pressure is provided between the oil outlet of the cylinder, which controls the lowering of the frame, and the control valve so as to control the descent of the frame at a constant speed and also to reduce its pressure to secure stability of operation of the control valve. In modern band sawing machines of relatively high speed and big horse power, with saw blades of improved quality and high efficiency, it has been actually realized that controlling the cutting-in speed at a constant rate is more effective than maintaining the total cutting load a constant value.

Other objects and many of the attendant advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered with the accompanying drawings, wherein:

FIG. 1 is a side elevation of a horizontal band sawing machine fitted with the control apparatus of the present invention;

FIG. 2 is a side elevation of the essential parts of FIG. I, on an enlarged scale, and serving as an explanation of the cutting load;

FIG. 3 is a sectional view showing the construction of the apparatus according to the invention;

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIG. 5 is a schematic detail view explaining the mechanism of the quantity control valve; and

FIG. 6 illustrates the function of the hydraulic system of the inventive apparatus.

FIG. 1 shows a bandsaw blade 7 mounted on a frame 5 which is pivoted at point 1 to a bed or base 3, the frame 5 being provided with a hydraulic cylinder assembly U (schematically shown in FIG. 2 with a simple oil or other hydraulic fluid circuit). It will be understood by those skilled in the art that reference to oil as a hydraulic fluid will be made herein only as a matter of example, and the term hydraulic assembly should be understood in its broadest sense.

FIG. 2 shows the blade 7 cutting a material M, with a simplified cutting-load distribution. P is the reactive force from the hydraulic fluid or oil flowing out of a cylinder 11, forming part of the assembly U, through a mouth or orifice 13, when a piston 9 descends inside the cylinder 11. W is the total weight of the frame 5, G being the center of gravity in the area of the material or workpiece M. In FIGS. 2 and 6, letters s illustrate the reactive force from the material M to the saw blade 7. K is the number of teeth in cutting action.

Considering these factors, the total cutting load can be derived as follows:

difference between the torques at W and P, around the pivot 1 distance between the pivot 1,

and the center of cutting The descent of the frame 5 corresponds to the descending speed of the piston 9, i.e., the fluid-flow speed from the orifice 13, which increases if P is raised or increased, and decreases accordingly if P is lowered or decreased.

Consequently, when the opening of the quantity control valve, i.e., the fluid-flow speed from the orifice 13 is kept constant, and the blade 7 is cutting with a constant feeding amount, and if then the cut length of the material M is increased or decreased, the cutting load is accordingly increased or decreased. Also, P, the fluid flowing out of the orifice I3 and the descending speed of the frame 5, i.e., the feeding amount tends to increase or decrease accordingly.

Also, if the strength of the material M increases or decreases, the cutting resistance will be respectively increased or decreased, and thus the cutting load will be similarly increased or decreased, acting on P and the fluid-flow speed i.e., to decrease or increase respectively the feeding amount.

In FIG. 3 the parts generally indicated by letter A constitute a mechanism to control and reduce the oil or hydraulic fluid pressure. A hydraulic case I5 is fixed appropriately to a machine body or base 14. Numeral 17 identifies a working piston slidably mounted in a cylinder 19. Numeral 20 is a spring held between one end of the working piston 17 and the inside bottom of the cylinder 19. The surface of the piston 17 (shown at 21 and 23, respectively, in elevation and in section) slidably contacts the inside of the cylinder 19, and at a recessed portion 25 of the piston 17 an oil passage 27 is provided which connects an oil passage 29 in the hydraulic case 15, which is connected to the oil passage 13, a recessed clearance 31 between the recessed portion 25 and the cylinder 19, and a clearance 33 between the right-hand piston head 23 and the other bottom of the cylinder 19.

The oil or hydraulic fluid passage 29 is partly closed by the piston 23, and as shown in the drawing, its opening increases or decreases as the piston 23 moves to the right-hand or the left-hand sides.

The mechanism generally indicated in FIGS. 3 and 5 by the letter B is a quantity control mechanism. In the inside of a cylinder 35, two quantity control hollow cylinders 37, 39 are fixably mounted with a common axis. AS shown in FIG. 5, the opposite ends of the cylinders 37, 39 are partly in contact, and the rest forms opposite circumferential surfaces 0, c with a clearance e therebetween, the latter clearance being zero at said contact point and gradually increasing to maximum at the position advanced by approximately only to decrease thereafter gradually toward the zero value.

A working plunger 47 is rotatably mounted with a close fit to the quantity control cylinders 37, 39, and fixed by an appropriately graduated handle 45 (see FIG. 3; the graduation or dial is not shown).

The plunger 47 has an oil passage 49 in its center, with one end open to an oil chamber connected to an oil passage 51 and to the clearance 33. The other end of the oil passage 49 is connected to an opening'53 which is positioned to meet said clearance e.

Total cutting load A clearance 55 between knife-edges 41, 43 is connected to an oil tank T (see FIG. 6), on the one hand, and, on the other, to the cylinder 19 where the spring 20 is contained, through an oil passage 57. Parts 59 are fixing pins for the cylinders 37, 39.

The function of the above-described mechanism shall now be explained with reference to FIGS. 3 and 6. Firstly, the opening of the quantity control assembly B is appropriately preset by means of the handle 45. Under certain working conditions, the opening of the oil passage 29 and the action of the spring 20 wiil keep the balance, and the oil or hydraulic fluid flowing out of the cylinder 11 is being pressed by the piston 9 back to the oil tank T through orifice 13, oil passage 29, clearance 31, oil passage 27, clearance 33, oil passages 51 and 49, opening 53, and clearance 55v If then the cut length of the material M increases, the reactive force P is reduced as explained before and the down stroke of the piston 9 inside the cylinder 11 is slowed down, resulting in less oil flowing through the passages 13, 29 to the clearance 31. The pressure inside the clearances 31, 33 is accordingly lowered, and the piston 17 is displaced to the right-hand side by means of the pressure of spring 20. Thus, the opening of the oil passage 29 is increased and the oil flow out of the cylinder 11 is increased, which helps the downstroke of the piston 9 and controls the decrease of cutting-in speed.

In a contrary sense, if the cut length decreases and the cutting-in speed increases, the downstroke of the piston 9 is accelerated and the pressure inside the clearances 31, 33 is raised so that the piston 17 is displaced toward the left-hand side. Thus the opening of the passage 29 is narrowed and the downstroke of the piston 9, and accordingly the increase of the cutting-in speed, is controlled.

It goes without saying that for materials of difierent hardness values, the mechanism functions in the same way as above to control the variation of the cutting speed.

As shown in FIG. 6, the oil pressure in passage 51, behind the pressure controlling and reducing mechanism A, is identified by P, while the outlet pressure, on the other side of the cylinders 37, 39, is denoted P The oil pressure P, is already reduced by the above-described operations and is thus remarkably low as compared to the prior systems where the cylinder is directly connected to the quantity control valve. Therefore, even when a conventional quantity control valve is used, its mechanism and operation can be simplified. In particular, the abovedescribed device connects the outlet of the quantity control mechanism B to the cylinder 19 where the spring 20 is contained, whereby the difference between the oil pressures P, and P is kept substantially constant, thus stabilizing the function of the quantity control valve.

As above described, the present invention consists, in one of its most important aspects, to control appropriately the descending speed of the frame of the band sawing machine by providing a hydraulic passage or connection, to connect the oil passage 13 which controls the descent of the frame to any quantity control valve, through the pressure controlling and reducing valve A, and by decreasing or increasing, as the case may be, the oil flow into said valve accordingly, as the descending speed of the frame increases or decreases. This procedural arrangement is not anticipated or even suggested by previous devices and arrangements.

By this method, even when the cut length becomes shorter or the hardness of the material to be cut drops, the cutting-in speed does not increase suddenly and thus the danger of breaking the saw blade is avoided.

Also, even when the cut length becomes longer or the hardness of the material increases, the cutting-in speed does not suddenly decrease, and the saw blade is not subjected to excessive wear. Furthermore, a lower pressure in the quantity control valve improves its operation.

The function of the quantity control mechanism B shall now be explained in more detail. The oil or hydraulic fluid flowing out of the clearance e between the cylinders 37, 39, after pasing through the pressure control and reducing mechanism A, the oil passages 51 and 49, and the outlet or opening 53, is

substantially free from the influence of viscosity variations due to the variation of oil temperature, by virtue of the knife edges 41, 43 at the outlet clearance 55. It is therefore possible to keep the oil flow constant by presetting the handle 45 and to exactly control the feeding amount. Also, the same effect is obtained in the case where the oil passage or orifice 13 is directly connected to the quantity control mechanism 8.

An oil passage 130, connected to the orifice 13, communicates with conventional pressure or propelling means Pa to supply pressurized hydraulic fluid through a pipe connection 140, having a check valve Va therein, which allows the fluid to flow in one direction, namely from Pa toward the pressure head of cylinder 11.

When one cutting-off operation is completed, the valve Va is opened (means Pa is actuated by any conventional power source such as a motor) and the pressurized fluid is allowed to flow through the pipe 14a, oil passage 13a and then into the pressure head of the cylinder 11, causing upward displacement of the piston 9, which in turn results in the upward pivotal movement of the frame 5, whereby the machine is ready to receive a new material M to be cut.

It is noted that during the upward displacement of the piston 9 the fluid supplied by the supply source Pa is also allowed to flow into the pressure control mechanism A, causing the same to be automatically adjusted to a position corresponding to the pressure of the fluid. It is to be noted, however, that the fluid flow into the mechanism A does not interfere with the upward displacement of the piston 9.

After new material M is set into a cutting position the motor driving the pressure means Pa is stopped, and the apparatus will repeat the cutting cycle as above described.

It should be noted that the mechanisms A and B are only schematically shown in FIG. 2 while more details appear in FIG. 6, and a sectional illustration is given in FIG. 3. The oil tank T is shown in both FIGS. 2 and 6.

Furthermore, the above-described function and effect is also obtainable in the commonly known case where the oil passage is arranged to double-act on the piston.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example described which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

Iclaim:

1. An apparatus to control the feeding amount in a hydraulically controlled band sawing machine, the latter having a pivotable frame supporting a band saw adapted operatively to engage a stationary material to be cut, and a hydraulic cylinder for selectively lifting and lowering a portion of said frame so as to pivot the same with respect to the material, the apparatus comprising, in combination, hydraulic pressure control means for said cylinder, valve means cooperating with said cylinder and controlling the quantity of the adjusted hydraulic fluid flowing through said valve means, the latter having an outlet with a knife-edge shape, a first hydraulic connection between the outlet of said cylinder and the inlet of said pressure control means, and a second hydraulic connection between the outlet of said pressure control means and the inlet of said valve means, wherein said pressure control means includes a spring-biased piston with at least one passage therein for the hydraulic fluid, which is narrowed in cross section as the action of said cylinder is accelerated urmn decrease of the cutting resistance and upon increase of the cutting-in speed, and vice versa, thus maintaining the pressure of the hydraulic fluid at a constant value when the same leaves said pressure control means.

2. The apparatus as defined in claim 1, wherein said passage of the piston is substantially transversal and communicates with a peripheral recessed tlearance in said piston as well as with a longitudinal passage therein which leads to said second hydraulic connection.

hydraulic connection.

6. The apparatus as defined in claim 1, further comprising a tank and propelling means for the hydraulic fluid, and means for providing an operative flow path for the hydraulic fluid from said cylinder to said tank by way of an inlet passage of said pressure control means, a recessed clearance in a springbiased displaceable control member thereof, an axial passage in the latter, a clearance beyond said control member, followed by said second hydraulic connection and said valve means, and back again. 

1. An apparatus to control the feeding amount in a hydraulically controlled band sawing machine, the latter having a pivotable frame supporting a band saw adapted operatively to engage a stationary material to be cut, and a hydraulic cylinder for selectively lifting and lowering a portion of said frame so as to pivot the same with respect to the material, the apparatus comprising, in combination, hydraulic pressure control means for said cylinder, valve means cooperating with said cylinder and controlling the quantity of the adjusted hydraulic fluid flowing through said valve means, the latter having an outlet with a knife-edge shape, a first hydraulic connection between the outlet of said cylinder and the inlet of said pressure control means, and a second hydraulic connection between the outlet of said pressure control means and the inlet of said valve means, wherein said pressure control means includes a spring-biased piston with at least one passage therein for the hydraulic fluid, which is narrowed in cross section as the action of said cylinder is accelerated upon decrease of the cutting resistance and upon increase of the cutting-in speed, and vice versa, thus maintaining the pressure of the hydraulic fluid at a constant value when the same leaves said pressure control means.
 2. The apparatus as defined in claim 1, wherein said passage of the piston is substantially transversal and communicates with a peripheral recessed clearance in said piston as well as with a longitudinal passage therein which leads to said second hydraulic connection.
 3. The apparatus as defined in claim 1, further comprising a bypass for the hydraulic fluid from said outlet of the valve means to the side of said piston acted upon by its biasing spring.
 4. The apparatus as defined in claim 1, wherein said valve means includes means for adjusting said outlet with the knife-edge shape with respect to a transversal passage in said valve means.
 5. The apparatus as defined in claim 4, wherein said transversal passage of the valve means communicates with a longitudinal passage therein which leads to said second hydraulic connection.
 6. The apparatus as defined in claim 1, further comprising a tank and propelling means for the hydraulic fluid, and means for providing an operative flow path for the hydraulic fluid from said cylinder to said tank by way of an inlet passage of said pressure control means, a recessed clearance in a spring-biased displaceable control member thereof, an axial passage in the latter, a clearance beyond said control member, followed by said second hydraulic connection and said valve means, and back again. 